Support custom filter strategy

[dnperfors]

Filtering is not really specified in the jsonapi.org specification and we have actually chosen an other filter strategy than is implemented in JsonApiDotNetCore.
Would it be possible/desirable to make the parsing of query strings more adaptable, so that we can override the ParseFilterQuery method to support queries like filter[attribute][lt]=value instead?

[jaredcnance]

I agree that this is an area where we need to be more flexible. What I would like to see happen is the parsing logic moved out of QuerySet into an injectable service. The way it is currently written, JsonApiContext implicitly depends on QuerySet which contains the parsing logic. There should be a service which parses the queries and returns the built QuerySet